Air sampling devices are generally used to determine the quantity and types of matter present in a gas (e.g., air or other gaseous atmospheres). For example, in a factory where materials are used that may be detrimental to human health, it may be desirable to determine the amount and types of matter present in the atmosphere so that factory workers are not exposed to unsafe or undesirable levels of airborne materials. In other examples, air sampling devices may be used in a variety of environments, including, but not limited to, office buildings, houses, hospitals, clean rooms, or outdoors.
Sampling devices conventionally include a collection device (e.g., a particle impaction device, microscope slide, petri dish, or other device) for collecting and retaining matter included in the gas being sampled. In use, the sampling device draws a gas (e.g., air) toward the collection device. Matter included in the gas impacts a substance or material (e.g., a collection medium) provided on or in the collection device, where the matter is retained until analysis can be performed. One known type of collection device is a cassette or cartridge type sampling device, such as the Air-O-Cell product manufactured by the assignee of the present application, Zefon International, Inc. of Ocala, Fla.
Conventional collection devices may not be ideally suited for sampling viable matter (e.g., organisms) such as mold spores, bacteria, viruses, and other viable matter. For example, some collection devices are designed to collect non-viable matter (e.g., particulate matter, asbestos, etc.), and utilize a collection medium (e.g., a dry filter or a tacky or sticky surface) that may dehydrate or desiccate viable matter. Dehydration may damage or destroy the viable matter, which may impede or prevent subsequent analysis or examination. Another difficulty with the use of such a collection medium is that removal of the viable matter may be difficult or impossible, which may prevent transfer of the viable matter to a growth medium (e.g., an agar medium) for further development or maturation.
Other types of known collection devices are designed to collect-viable matter directly into a growth medium. For example, a collection device such as a petri dish may include an agar medium (e.g., malt extract agar, potato extract agar, etc.). In use, viable matter is impacted directly into the growth medium, where the viable matter develops or matures due to the presence of nutrients in the growth medium. The use of growth medium as an impaction material may present a variety of difficulties. For example, agar media must typically be kept cool during storage and shipping by refrigeration or similar methods. Even with refrigeration, agar media must be used within a relatively short period of time (e.g., 30 days). Accordingly, collection devices using agar media have a relatively short “shelf life” and must either be used within the life of the product or discarded.
Another difficulty with the use of growth media in collection devices relates to the fact that certain types of viable matter require specific types of agar media. For example, certain types of viable matter may require a malt extract agar, blood agar, soy agar, etc. It may therefore be necessary to obtain a number of air samples in a variety of different growth media types to ensure that the types of viable matter present in the air are collected in appropriate growth media. Removal of viable matter from one growth medium and transfer of the viable matter to a different growth medium is difficult or impossible. Collecting a number of air samples may not be practical or feasible in certain situations. For example, if an individual has a single sampling device and wishes to obtain multiple air samples during a particular time period, such sampling may be impossible given the time required to obtain a sample. Even where obtaining multiple samples is possible, such sampling is inefficient in that either multiple samples must be taken sequentially or multiple air sampling devices must be used concurrently.
Yet another difficulty with the use of conventional collection devices is that the collection devices may become contaminated with continued use. For example, after sampling is complete, the collection medium (e.g., agar medium) is removed from the collection device and the collection device is cleaned. Remnants of past samples and media may remain after cleaning, which may affect results of subsequent sampling.
Yet still another difficulty with conventional collection devices is that sampling may not achieve desired results. For example, if the amount of time for a particular sample is too long, there may be an excess of sampled matter, which will prevent growth of viable matter and counting of viable matter due to overcrowding of the sample medium. If sampling time is too short, there may be insufficient amount of sampled matter for analysis. In such a situation, the possibility of obtaining a false reading may be greatly enhanced.
Yet further still another difficulty with conventional collection devices is that the user must place an appropriate amount of collection medium on or in the collection device. Variability due to human error in the thickness and amount of collection medium may affect results of subsequent sampling. For example, overloading the collection device with collection medium may alter the gas flow characteristics of the device (e.g., the collection medium may block an air inlet) or collection efficiency may be reduced.